Although you may not have heard of equine peritonitis, a 1997 veterinary survey of chronic colic cases — horses with signs of colic for three days or longer — showed that 16% of these were caused by it.
Peritonitis is a potentially life-threatening illness for horses and in the days before modern medication and sophisticated surgery, most sufferers did not survive. Now the outlook is better, but not every case will recover.
What is peritonitis?
Within the abdomen, a thin, shiny protective membrane called the peritoneum covers the intestines. This membrane also lines the insides of the walls of the abdominal cavity, formed by the muscles of the abdomen, flank and back. It provides a smooth, healthy surface for the various pieces of bowel to slide over each other, so they do not become entangled or stuck together. It also produces fluid (about 60ml per hour in a horse) that helps lubricate the contents of the abdomen and has some ability to combat infection.
When the peritoneum becomes inflamed, sore or irritated, the condition is known as peritonitis. Infection can produce pus or localised abcesses and severe cases may potentially succumb from shock.
Many different conditions can cause peritonitis and it can occur in horses of all ages, types and gender. There may be some underlying problem, such as previous abdominal surgery, or trauma, such as a stake wound. Damage that occurred during breeding or foaling may be responsible, and peritonitis can be a rare complication following castration. It can also develop as a result of a tumour or worms. The precise cause is often unidentified.
Spotting the clues
Signs will vary depending on the nature and extent of the condition.
A localised peritonitis affecting a small area of the abdomen, with an abscess walled away, may grumble on for a long time and can be hard to pinpoint. Such cases of chronic peritonitis may be hard to diagnose, as they show only vague signs such as weight loss.
However, a very sudden (peracute) episode of severe generalised peritonitis, which may follow on from the rupture of the stomach or other part of the bowel, can be fatal within a few hours. In these cases, the horse may be found dead or be seen to be very ill with severe shock and a painful abdomen.
When the bowel has actually ruptured there is nothing that can be done. The kindest thing is to put the horse down as quickly as possible. Thankfully, the less severe cases of peritonitis are much more treatable.
What to look out for
Colic or abdominal pain is the most obvious sign of peritonitis in the horse.
Other potential signs can include:
- A raised heart rate
- A raised temperature
- Reduced gut sounds
- Weight loss
- Loss of appetite
- Dullness of the coat and eyes
- Reluctance to move
This veterinary feature was first published in Horse & Hound